1. Field of the Invention
The present invention relates to techniques for sealing cylindrical bodies to circumscribing conduits and, specifically, to a self-locating seal assembly for sealing a well string within the bore of a surrounding well conduit.
2. Description of the Prior Art
Sealing devices of various kinds are used in well working operations, and in the production of a well. For example, in downhole cementing procedures, seal assemblies are used to control the placement of cement and the maintenance of pressure to accomplish cementing operations. Seal assemblies in the form of packers are known for isolating formations for treatment, or for isolating segments of liner or casing for squeeze cementing, for example. Packers are also used routinely for sealing production strings to liner or casing to define flow paths from producing formations to the surface.
Prior art seal assemblies of the type used in positioning and bonding a liner in a casing have typically included radially moving dogs for latching the seal assembly within the liner. For instance, U.S. Pat. No. 4,281,711, issued Aug. 4, 1981, to Braddick et al, shows a seal assembly used in bonding a liner within a casing. The liner is made up to include a sequence of tubular members threaded together. One of the tubular members or subs is provided with an internal recess, usually a circumferential groove, in proximity to a landing shoulder within the sub. The seal assembly is landed on the landing shoulder within the liner sub and has radially moving dogs which are actuated to latch the seal assembly into the internal recess provided in the pipe sub.
In U.S. Pat. No. 4,657,077, issued Apr. 14, 1987, to Sidney K. Smith, Jr. et al., for "Locking Production Seal Assembly," a production assembly is shown which is used, for example, to latch a tubing string within the bore of a surrounding conduit. The device features setting dogs which are radially actuated to move into engagement with the internal recess provided in the surrounding conduit. U.S. Pat. No. 4,406,324, issued Sept. 27, 1983, and assigned to the assignee of the present invention also shows a seal assembly with latching dogs for engaging a surrounding recess.
In the prior art seal assemblies, an outer sleeve was usually carried about a sliding inner mandrel. The latching dogs moved in windows or openings in the outer sleeve for latching engagement with the recesses provided in the surrounding conduit. During well bore operations, when pressure is on the tool, the latching dogs were subjected to loads which could damage the exterior surface of the sliding mandrel. The damaged mandrel could, in turn, damage that portion of the seal assembly used to seal between the mandrel and the surrounding conduit.
It is an object of the present invention to provide a seal assembly which is self-locating and which does not require a locating shoulder in the pipe sub of the surrounding conduit into which the assembly is to be latched.
Another object of the invention is the provision of a seal assembly with latching dogs and a sliding mandrel, the assembly having a unique internal seal body which cooperates with the latching dogs to prevent damage to the exterior surface of the sliding mandrel during well bore operations.
Additional objects, features and advantages will be apparent in the written description which follows.